The present invention relates to a multi-chip module in which a plurality of semiconductor chips are mounted on a mounting board.
In recent years, mobile phones, note type computers, PDA (Personal Digital Assistance) or the like are rapidly coming into wide use, while miniaturization and weight reduction and higher performance of these consumer-oriented electronic systems are rapidly being pursued. In order to realize these, there is a need for a technology for densely packing semiconductor devices, such as a CPU, microprocessor, logic, and memory, and passive electronic components and assembling them into a system module.
Although an ultimate aspect of the system module is a system-on-chip in which all devices are made into a single chip, it is difficult to make different devices into a chip at the same time, and thus there is fear for a reduction in yield. Further, such a system module is made on orders for each of products and tends to be manufactured in small volumes with different configurations. Therefore, there is a problem that newly designing of such products from the stage of devices may be not cost-justified. Thus, the technology development of MCM (Multi-Chip Module) is actively pursued, in which a plurality of separately manufactured chips are densely mounted with wiring length as short as possible to assemble into one system module.
An example of conventional MCM's is described in JP-A-10-126044 specification, which discloses an MCM structure, wherein a plurality of semiconductor chips are flip-chip mounted on a base board via solder and a sealing resin is flowed between the semiconductor elements and the base board.
Further, JP-A-2000-196008 specification discloses a multi-chip type semiconductor device, in which semiconductor chips of not less than three are arranged on a board in a planar manner, electrical connections between the chips are made with fine lines, and the whole of the semiconductor chips and fine lines are covered with a sealing resin, and then a ball grid array which becomes as external electrodes is formed on a back surface of the board.
However, any of JP-A-10-126044 and JP-A-2000-196008 specification does not disclose how to improve the reliability of the whole multi-chip modules to thermal stress or the like.
Therefore, the invention has an object to provide a multi-chip module having high reliability to thermal stress or the like.